Semiconductor processing reactive precursor valve assembly

ABSTRACT

The invention includes chemical vapor deposition methods, including atomic layer deposition, and valve assemblies for use with a reactive precursor in semiconductor processing. In one implementation, a chemical vapor deposition method includes positioning a semiconductor substrate within a chemical vapor deposition chamber. A first deposition precursor is fed to a remote plasma generation chamber positioned upstream of the deposition chamber, and a plasma is generated therefrom within the remote chamber and effective to form a first active deposition precursor species. The first species is flowed to the deposition chamber. During the flowing, flow of at least some of the first species is diverted from entering the deposition chamber while feeding and maintaining plasma generation of the first deposition precursor within the remote chamber. At some point, diverting is ceased while feeding and maintaining plasma generation of the first deposition precursor within the remote chamber. Other aspects and implementations are contemplated.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a DIV of Ser. No. 10/691,769 filed Oct. 22, 2003which is a DIV of Ser. No. 10/107,609 filed Mar. 26, 2002, now U.S. Pat.No. 6,800,134.

TECHNICAL FIELD

This invention relates to chemical vapor deposition methods, includingatomic layer deposition, and to valve assemblies for use with a reactiveprecursor in semiconductor processing.

BACKGROUND OF THE INVENTION

Semiconductor processing in the fabrication of integrated circuitrytypically includes the deposition of layers on semiconductor substrates.Exemplary processes include physical vapor deposition (PVD) and chemicalvapor deposition (CVD). In the context of this document, “CVD” includesany process, whether existing or yet-to-be developed, where one or morevaporized chemicals is fed as a deposition precursor for reaction andadherence to a substrate surface. By way of example only, one such CVDprocess includes atomic layer deposition (ALD). With typical ALD,successive mono-atomic layers are adsorbed to a substrate and/or reactedwith the outer layer on the substrate, typically by successive feedingof different precursors to the substrate surface.

Chemical vapor depositions can be conducted within chambers or reactorswhich retain a single substrate upon a wafer holder or susceptor. One ormore precursor gasses are typically provided to a shower head within thechamber which is intended to uniformly provide the reactant gassessubstantially homogeneously over the outer surface of the substrate. Theprecursors react or otherwise manifest in a deposition of a suitablelayer atop the substrate. Plasma enhancement may or may not be utilized,and either directly within the chamber or remotely therefrom.

In certain chemical vapor deposition processes, including ALD,precursors are pulsed or otherwise intermittently injected into thereactor for reaction and/or deposition onto a substrate. In many cases,it is highly desirable to turn the individual precursor flows on and offvery quickly. For example, some deposition processes utilize plasmageneration of a precursor in a chamber remote from the depositionchamber. As the precursor leaves the remote plasma generation chamber,such typically converts to a short lived, non-plasma desired activestate intended to be maintained for reaction in the deposition chamber.Yet plasma generation in the remote chamber is very pressure dependent,and the plasma typically ceases in the remote chamber whenswitching/pulsing the active species flow to the chamber. Accordingly,such process are expected to utilize pulsed remote plasma generation,and which may not be practical.

The invention was motivated in overcoming the above-described drawbacks,although it is in no way so limited. The invention is only limited bythe accompanying claims as literally worded without interpretative orother limiting reference to the specification or drawings, and inaccordance with the doctrine of equivalents.

SUMMARY

The invention includes chemical vapor deposition methods, includingatomic layer deposition, and valve assemblies for use with a reactiveprecursor in semiconductor processing. In one implementation, a chemicalvapor deposition method includes positioning a semiconductor substratewithin a chemical vapor deposition chamber. A first deposition precursoris fed to a remote plasma generation chamber positioned upstream of thedeposition chamber, and a plasma is generated therefrom within theremote chamber and effective to form a first active deposition precursorspecies. The first species is flowed to the deposition chamber. Duringthe flowing, flow of at least some of the first species is diverted fromentering the deposition chamber while feeding and maintaining plasmageneration of the first deposition precursor within the remote chamber.At some point, diverting is ceased while feeding and maintaining plasmageneration of the first deposition precursor within the remote chamber.

In one implementation, a chemical vapor deposition method includespositioning a semiconductor substrate within a chemical vapor depositionchamber. A first deposition precursor is fed to the chamber through atleast a portion of a rotatable cylindrical mass of a valve assembly.During the flowing, flow of at least some of the first depositionprecursor is diverted from entering the deposition chamber by rotatingthe cylindrical mass in a first rotational direction. At some pointwhile diverting is occurring, the cylindrical mass is rotated in thefirst rotational direction effective to cease said diverting.

In one implementation, a valve assembly for a reactive precursor to beused in semiconductor processing includes a valve body having at leastone inlet and at least two outlets. The inlet is configured forconnection with a reactive precursor source. A first of the outlets isconfigured for connection with a feed stream to a semiconductorsubstrate processor chamber. A second of the outlets is configured fordiverting precursor flow away from said chamber. The valve body includesa first fluid passageway therein extending between the inlet and thefirst outlet. The valve body has a second fluid passageway extendingbetween the first fluid passageway and the second outlet. A controlplate and/or generally cylindrical mass is mounted for at least limitedrotation within the body proximate the first and second passageways.Such includes an arcuate region at least a portion of which is receivedwithin the first passageway. The arcuate region includes a first regionhaving an opening extending therethrough and which is positionable intoa first selected radial orientation to provide the inlet and the firstoutlet in fluid communication with one another through the firstpassageway while restricting flow to the second passageway. The arcuateregion includes a second region positionable into the first radialorientation to provide the inlet and second outlet in fluidcommunication through the first and second passageways while restrictingflow to the first outlet.

Other aspects and implementations are contemplated.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic illustration of a preferred embodimentimplementation of an aspect of the invention.

FIG. 2 is a diagrammatic sectional view taken through line 2—2 in FIG. 3of a valve assembly in accordance with an aspect of the invention, andin one operational orientation.

FIG. 3 is a sectional view taken through line 3—3 in FIG. 2.

FIG. 4 is a sectional view taken through line 4—4 in FIG. 5, and is ofthe FIG. 2 valve assembly in another operational orientation.

FIG. 5 is a sectional view taken through line 5—5 in FIG. 4.

FIG. 6 is a diagrammatic sectional view taken of an alternate embodimentvalve assembly in accordance with an aspect of the invention, and in oneoperational orientation.

FIG. 7 is an enlarged sectional view taken through line 7—7 in FIG. 6.

FIG. 8 is an enlarged perspective view of a component of the FIG. 6valve assembly.

FIG. 9 is a diagrammatic sectional view of the FIG. 6 valve assembly inanother operational orientation.

FIG. 10 is an enlarged sectional view taken through line 10—10 in FIG.9.

FIG. 11 is an enlarged diagrammatic sectional view of the FIG. 6 valveassembly in yet another operational orientation.

FIG. 12 is an enlarged diagrammatic sectional view of the FIG. 6 valveassembly in still another operational orientation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

A first embodiment chemical vapor deposition method is describedinitially with reference to FIG. 1. Such depicts a chemical vapordeposition chamber 12 having a semiconductor substrate 14 positionedtherein. In the context of this document, the term “semiconductorsubstrate” or “semiconductive substrate” is defined to mean anyconstruction comprising semiconductive material, including, but notlimited to, bulk semiconductive materials such as a semiconductive wafer(either alone or in assemblies comprising other materials thereon), andsemiconductive material layers (either alone or in assemblies comprisingother materials). The term “substrate” refers to any supportingstructure, including, but not limited to, the semiconductive substratesdescribed above.

A remote plasma generation chamber 16 is positioned upstream ofdeposition chamber 12. Any existing or yet-to-be-developed remote plasmageneration is contemplated. Plasma generator 16 is fed by an inletstream 18 for feeding some suitable first deposition precursor thereto.A valve assembly 20 is depicted as being received intermediate plasmagenerator 16 and deposition chamber 12. An out-feed line 22 from plasmagenerator 16 is depicted as being an in-feed line to valve assembly 20.An out-feed line 24 feeds from valve assembly 24 to deposition chamber12, and another out-feed line 26 from valve assembly 20 is directed awayfrom feeding to deposition chamber 12. More than the illustrated valveassembly input and outputs are of course contemplated.

Valve assembly out-feed line 24 includes exemplary additional in-feedlines 28 and 30. Such might be configured for providing additionaldeposition precursors and/or purge gasses for separate or combined flowwith precursor from valve assembly 20 to deposition chamber 12. More orfewer downstream lines could be included, of course, as well as beingdirectly provided to chamber 12 apart from stream 24.

The above-described and illustrated embodiment of FIG. 1 is but oneexample diagrammatic depiction usable in carrying out methodical aspectsof the invention. Any other processing in accordance with the methodclaims as literally worded without limiting or interpretative referenceto the specification or drawings is also of course contemplated.

With semiconductor substrate 14 positioned within deposition chamber 12,a first deposition precursor is fed to remote plasma generation chamber16. A plasma is generated therefrom within the remote chambereffectively to form a first active deposition precursor species forprovision to deposition chamber 12. Such first species is flowed todeposition chamber 12 via line 22, valve assembly 20 and line 24. Duringsuch flowing, the flow of at least some of the first species is divertedfrom entering deposition chamber 12, all while feeding and maintainingplasma generation of the first deposition precursor within the remotechamber. For example in the preferred embodiment, valve assembly 20 isoperated for diverting the flow of at least some of the first speciesinto line 26 as opposed to line 24. In the depicted preferredembodiment, diverting and ceasing thereof is controlled by a singlevalve assembly 20 located downstream of remote chamber 16 and upstreamof deposition chamber 12 as respects flow of the first depositionprecursor.

In one preferred embodiment, the diverting is effective to divertsubstantially all of the first species from entering the depositionchamber, and all while feeding and maintaining plasma generation of thefirst deposition precursor within the remote chamber. In other words inthe depicted preferred embodiment, line 24 is effectively completelyblocked off by valve assembly 20, with line 26 being provided in an openstate by valve assembly 20.

In one preferred embodiment, the method is atomic layer deposition, withchamber 12 comprising an atomic layer deposition chamber. Flowing of thefirst species to chamber 12 and substrate 14 therein is therebyeffective to form a first monolayer on the substrate. In one preferredatomic layer deposition while such diverting is occurring, for exampleinto line 26, a purge gas is flowed to chamber 12, and all while feedingand maintaining plasma generation of the first deposition precursorwithin the remote chamber. For example in the FIG. 1 depictedembodiment, a purge gas could be flowed to chamber 12 via one or both oflines 28 and 30. Further in one preferred atomic layer deposition methodin accordance with an aspect of the invention, after flowing the purgegas and while diverting, a second deposition precursor different fromthe first deposition precursor is fed to deposition chamber 12 effectiveto form a second monolayer on the first monolayer, and all while feedingand maintaining plasma generation of the first deposition precursorwithin remote chamber 16. Again in the depicted exemplary embodiment,one or both of lines 28 and 30 could be utilized for the same. Furtherin accordance with one preferred atomic layer deposition methodimplementation, after forming the second monolayer and while diverting,a purge gas (the same or different from the first-described purge gas)is flowed to the chamber all while feeding and maintaining plasmageneration of the first deposition precursor within remote chamber 16.

Regardless, a chemical vapor deposition method in accordance with anaspect of the invention contemplates ceasing the diverting all whilefeeding and maintaining plasma generation of the first depositionprecursor within the remote chamber. In one embodiment where thediverting constitutes ceasing essentially all flow of the first speciesfrom entering the deposition chamber, such ceasing of the diverting willresult in the resumption of first species flow to chamber 12. In oneembodiment where such diverting does not constitute diversion of all ofthe first species from entering the deposition chamber, such ceasing ofthe diverting will result in an increased rate of flow of the firstspecies to chamber 12.

In one atomic layer deposition method in accordance with an aspect ofthe invention, another monolayer is effectively formed on the substrate.Such monolayer may be the same as the first monolayer. Such monolayermay be a third monolayer formed on the second monolayer, which is thesame as either the first or second monolayers, or some reaction productthereof.

In one considered aspect, the flowing of the first species to depositionchamber 12 can be considered as being at subatmospheric pressure, andcomprises flow into a first passageway inlet, for example the inlet toline 24 exiting valve assembly 20. The diverting can be considered ascomprising flow into a second passageway inlet, for example into line 26from valve assembly 20. In accordance with one aspect of the invention,the method comprises maintaining pressure of the first inlet and thesecond inlet within 500 mTorr, and more preferably within 100 mtorr,from one another during the flowing and the diverting. By way of exampleonly, maintaining such pressure control during the entirety of thedeposition process can facilitate maintenance and control of plasmawithin remote generator 16. Yet in one preferred embodiment, theinvention contemplates keeping the pressure of the first inlet and thesecond inlet greater than 500 mTorr from one another during the flowingand the diverting. Subatmospheric pressure within the exemplary system,as well as within plasma generator 16, is intended to be maintained inthe preferred embodiment primarily by line 26 and an out-feed line 32from chamber 12 to the same or different subatmospheric vacuum pressuresources.

In one exemplary preferred embodiment, particularly where the divertingis of all flow from entering line 24, the diverting preferably takesplace over a time period sufficient to reduce the risk of temporarilyisolating vacuum pressure from plasma generator 16, which mightotherwise cause extinguishing of the plasma. In one preferredembodiment, the diverting takes from 0.1 second to 1.0 second fromstaring the diverting of the first species to total diversion of thefirst species, and in another embodiment takes more than 1.0 second.

In one preferred embodiment, the diverting, for example utilizing valveassembly 20, comprises rotating a cylindrical valve mass. In onepreferred embodiment, the diverting, for example utilizing valveassembly 20, comprises rotating a valve plate which may or may notconstitute a cylindrical valve mass. For example, and by way of exampleonly, such a valve plate might be square or rectangular incross-section, as opposed to being substantially round in at least onecross-section.

In one exemplary implementation, the diverting, for example using valveassembly 20, can comprise pivoting a valve flap, and in one exemplaryimplementation can comprise straight linearly sliding of a divertingvalve mass.

By way of examples only, two exemplary valve assembly constructionsusable in carrying out methodical aspects of the invention are describedwith reference to FIGS. 2–12. The invention also contemplates valveassemblies for use in semiconductor processing with reactive precursorsindependent of any method claimed or described herein. The respectivemethod claim families and apparatus claim families stand as literallyworded, without reference to the other. In other words, the concludingapparatus claims are not limited by the method claims, nor are theconcluding method claims limited by any attribute of the apparatusclaims, unless literal language appears in such claims, and without anylimiting or interpretative reference to the specification or drawings.

An exemplary first embodiment semiconductor processing reactiveprecursor valve assembly is described with reference to FIGS. 2–5, andis indicated generally with reference numeral 36. FIGS. 2 and 3 depictassembly 36 in one exemplary operational configuration, while FIGS. 4and 5 depict assembly 36 in another operational configuration. Valveassembly 36 comprises a valve body 37 having at least one inlet 38 andat least two outlets 40 and 42. Inlet 38 is configured for connectionwith a reactive precursor source. First depicted outlet 40 is configuredfor connection with a feed stream to a semiconductor substrate processorchamber, and second outlet 42 is configured for diverting precursor flowaway from such chamber. Valve body 37 comprises a first fluid passageway44 therein extending between inlet 38 and first outlet 40. Valve body 37also comprises a second fluid passageway 46 extending between firstfluid passageway 44 and second outlet 42. In the depicted preferredembodiment, first passageway 44 extends in a straight axial line throughvalve body 37 from inlet 38 to outlet 40, and second passageway 46extends in a straight axial line through valve body 37 perpendicular toand from first passageway 44 to second outlet 42. Either might be of anyconstant or variable cross sectional shape, and/or size.

A control mass 48 is mounted for at least limited rotation within body37 proximate the first and second passageways. In one implementation,control mass 48 is in the form of a control plate. In oneimplementation, control mass 48 is in the form of a generallycylindrical mass. In the depicted preferred embodiment, control mass 48is in the form of both a control plate which is round and in the form ofa generally cylindrical mass. The depicted embodiment shows controlplate 48 mounted for rotation about a central axis 50 constituting a rodwithin body 37 which projects into control plate 48 for rotationalsupport. Accordingly and further in a preferred embodiment, the axis ofrotation 50 is oriented generally parallel with respect to first axialstraight line 44, and accordingly with respect to a direction ofprecursor flow proximate the valve plate. Valve/control plate 48 is alsoin the preferred embodiment mounted for 360° of rotation within body 37.

Control plate/cylindrical mass 48 includes an arcuate region 52 (FIG.3), at least a portion of which is received within first passageway 44.Arcuate region 52 includes a first region 54 having an opening 58extending through the plate and positionable into a first selectedradial orientation 60 (as shown in FIGS. 2 and 3) to provide inlet 38and first outlet 40 in fluid communication with one another throughfirst passageway 44 while restricting flow to second passageway 46. Inthe preferred depicted embodiment, first region 54 is configured toblock all fluid flow from entering second fluid passageway 46 when infirst selected radial orientation 60. Further in the preferredembodiment, opening 58 has a maximum cross-section which is at least aslarge of that of first passageway 44 proximate control plate 48. Furtherin the preferred embodiment, opening 58 has a cross sectional shapewhich is the same as that of that of first passageway 44 proximatecontrol plate 48 (i.e., circular). Alternately, the opening could have across sectional shape which is different (i.e., any of elliptical,square, rectangular, triangular, s-shaped, circular, etc.) from that ofthe first passageway (i.e., any different of elliptical, square,rectangular, triangular, s-shaped, circular, etc.). Preferably in suchinstance, the opening has a maximum cross-section which is at least aslarge of that of the first passageway proximate the control plate.

Arcuate region 52 includes a second region 56 positionable into firstradial orientation 60 (FIGS. 4 and 5) to provide inlet 38 and secondoutlet 42 in fluid communication with one another through firstpassageway 44 and second passageway 46 while restricting flow to firstoutlet 40. In the depicted preferred embodiment, second region 56 isconfigured to block substantially all fluid flow to first outlet 40 whenin the first selected radial orientation 60. In the depicted preferredembodiment, second region 56 includes an arcuate surface 62 (FIG. 4)configured to direct fluid flow 90° from a flow direction to plate 48. Aflat surface 64 is connected with arcuate surface 62 and extends tosecond passageway 46 when in first radial position 60 (FIGS. 4 and 5).In the depicted preferred embodiment, second region 56 does not includea hole extending through plate 48.

As shown, arcuate region 52 is in the form of an annulus, including aplurality of alternating first and second regions 54 and 56. At leastthree of the first regions and at least three of the second regions areincluded in one preferred embodiment.

Another exemplary embodiment semiconductor processing reactive precursorvalve assembly 70 is depicted in various operational states in FIGS.6–12. Assembly 70 includes a valve body 71 having at least first andsecond inlets 72, 73, and at least two outlets 74, 75. First and secondinlets 72, 73 are configured for connection with distinct gas sources atleast one of which is a deposition precursor. A first of the outlets,for example outlet 74, is configured for connection with a feed streamto a semiconductor substrate processor chamber. A second of the outlets,for example outlet 75, is configured for diverting gas flow away fromsuch chamber. In the depicted preferred embodiment, first and secondinlet 72, 73 to valve body 71 are opposed 180° from one another, as arefirst and second outlets 74, 75. Further, first and second inlets 72, 73to valve body 71 are oriented at 90° from first and second outlets 74,75 from body 71.

A generally cylindrical mass 76 is mounted for at least limited rotationwithin body 71. Such comprises, a first longitudinal portion 77 and asecond longitudinal portion 78 proximate thereto (FIGS. 6 and 8). In thedepicted preferred embodiment, the first and second longitudinalportions are substantially mirror images of one another, with generallycylindrical mass 76 comprising two overlapping half cylindrical-shapedsections.

First longitudinal portion 77 is configured to provide first inlet 72 influid communication with first outlet 74 when in a first selected radialorientation (i.e., that radial orientation depicted in FIGS. 6 and 7).First longitudinal portion 77 is also configured to provide first inlet72 in fluid communication with second outlet 75 when in a secondselected radial orientation (i.e., as shown in FIGS. 9 and 10).

Further, second longitudinal portion 78 is configured to provide secondinlet 73 in fluid communication with first outlet 74 when in the secondselected radial orientation (i.e., that of FIGS. 9 and 10). Secondlongitudinal portion 78 is also configured to provide second inlet 73 influid communication with second outlet 75 when in the first selectedradial orientation (i.e., FIGS. 6 and 7).

FIGS. 11 and 12 diagrammatically illustrate respective third and fourthselected radial orientations. As shown in the exemplary third radialorientation (FIG. 11), first longitudinal portion 77 is configured toprovide first inlet 72 in fluid communication with both first and secondoutlets 74, 75. Further, second longitudinal portion 78 is configured toprovide second inlet 73 in fluid communication with both first andsecond outlets 74, 75 in the third selected radial orientation. The samerelationships exist in the FIG. 12 fourth selected radial orientation,which is 180° from the third selected radial orientation.

The above-described structures are, of course, usable with or withoutremote plasma generation. Further, the rotational speed, size, shape andplacement of the respective inlet and outlet openings can be used todetermine the duty cycle and pulse length of the various gas on/offstates in the various embodiments.

Additional methods are contemplated in accordance with aspects of theinvention. In one implementation, an atomic layer deposition methodincludes positioning a semiconductor substrate within an atomic layerdeposition chamber. A first deposition precursor is fed to a remoteplasma generation chamber positioned upstream of the deposition chamberand a plasma is generated therefrom within the remote chamber andeffective to form a first active deposition precursor species. The firstspecies is flowed to the substrate through at least a portion of arotatable cylindrical mass of a valve assembly effective to form a firstmonolayer on the substrate.

During the flowing, the flow of substantially all the first species isdiverted from entering the deposition chamber with the rotatablecylindrical mass, while feeding and maintaining plasma generation of thefirst deposition precursor within the remote chamber. While diverting, apurge gas is flowed to the chamber through at least a portion of therotatable cylindrical mass of the valve assembly while feeding andmaintaining plasma generation of the first deposition precursor withinthe remote chamber. After flowing the purge gas, the cylindrical mass isrotated effective to cease such diverting while feeding and maintainingplasma generation of the first deposition precursor within the chamber,and ultimately, effective to form another monolayer on the substrate. Anintervening monolayer may or may not be formed. In one implementation,the portion through the rotatable cylindrical mass of the valve assemblythrough which the first species flows is different from the portionthrough the rotatable cylindrical mass of the valve assembly throughwhich the purge gas flows (for example, and by way of example only,using the structure of FIGS. 2–5).

In yet another considered aspect of the invention, a chemical vapordeposition method is contemplated regardless of remote plasmageneration. In accordance with this aspect of the invention, asemiconductor substrate is positioned within a chemical vapor depositionchamber. A first deposition precursor is fed to the chamber through atleast a portion of a rotatable cylindrical mass of a valve assembly.During the flowing, the flow of at least some of the first depositionprecursor is diverted from entering the deposition chamber by rotatingthe cylindrical mass in a first rotational direction (i.e., rotationaldirection 85 as shown in FIG. 5 if using such apparatus). During thediverting, the cylindrical mass is rotated in the first rotationaldirection effective to cease such diverting (i.e., to place the FIGS.2–5 embodiment in the position depicted by FIGS. 2 and 3 if using suchapparatus). Atomic layer deposition and remote plasma generation withina chamber remote from the deposition chamber are also, of course,contemplated.

Regardless and in ene preferred embodiment, rotation of the rotatablecylindrical mass in the first rotational direction is maintained fromthe feeding to the diverting to the ceasing of such diverting. Suchmaintaining might be at a variable rate of rotation in the firstrotational direction among the feeding to the diverting to the ceasingof said diverting, or might be at a constant rate of rotation. Furtherand regardless, the invention contemplates in one aspect continuing suchrotation in the first direction after ceasing effective to start saidfeeding again.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A semiconductor processing reactive precursor valve assemblycomprising: a valve body having at least first and second inlets and atleast two outlets, the first and second inlets being configured forconnection with distinct gas sources at least one of which is adeposition precursor, a first of the outlets being configured forconnection with a feed stream to a semiconductor substrate processorchamber, a second of the outlets being configured for diverting gas flowaway from said chamber; a generally cylindrical mass mounted for atleast limited rotation within the body; the generally cylindrical masscomprising a first longitudinal portion configured to provide the firstinlet in fluid communication with the first outlet when in a firstselected radial orientation and to provide the first inlet in fluidcommunication with the second outlet when in a second selected radialorientation; and the generally cylindrical mass comprising a secondlongitudinal portion proximate the first longitudinal portion and whichis configured to provide the second inlet in fluid communication withthe first outlet when in the second selected radial orientation and toprovide the second inlet in fluid communication with the second outletwhen in the first selected radial orientation.
 2. The assembly of claim1 wherein the first and second longitudinal portions are substantialmirror images of one another.
 3. The assembly of claim 1 wherein thegenerally cylindrical mass comprises two overlapping half cylindricalshaped sections.
 4. The assembly of claim 1 wherein the firstlongitudinal portion is configured to provide the first inlet in fluidcommunication with both the first and second outlets when in a thirdselected radial orientation.
 5. The assembly of claim 4 wherein thefirst longitudinal portion is configured to provide the first inlet influid communication with both the first and second outlets when in afourth selected radial orientation which is 180° from the third selectedradial orientation.
 6. The assembly of claim 1 wherein the secondlongitudinal portion is configured- to provide the second inlet in fluidcommunication with both the first and second outlets when in a thirdselected radial orientation.
 7. The assembly of claim 6 wherein thesecond longitudinal portion is configured to provide the second inlet influid communication with both the first and second outlets when in afourth selected radial orientation which is 180° from the third selectedradial orientation.
 8. The assembly of claim 1 wherein the firstlongitudinal portion is configured to provide the first inlet in fluidcommunication with both the first and second outlets when in a thirdselected radial orientation and the second longitudinal portion isconfigured to provide the second inlet in fluid communication with boththe first and second outlets when in the third selected radialorientation.
 9. The assembly of claim 8 wherein the first longitudinalportion is configured to provide the first inlet in fluid communicationwith both the first and second outlets when in a fourth selected radialorientation which is 180° from the third selected radial orientation andthe second longitudinal portion is configured to provide the secondinlet in fluid communication with both the first and second outlets whenin the fourth selected radial orientation.
 10. The assembly of claim 1wherein the first and second inlets to the valve body are 180° opposed.11. The assembly of claim 1 wherein the first and second outlets fromthe valve body are 180° opposed.
 12. The assembly of claim 1 wherein,the first and second inlets to the valve body are 180° opposed; and thefirst and second outlets from the valve body are 180° opposed.
 13. Theassembly of claim 1 wherein at least one inlet to the valve body isoriented at 90° from at least one outlet from the body.
 14. The assemblyof claim 1 wherein, the first and second inlets to the valve body are180° opposed; the first and second outlets from the valve body are 180°opposed; and the first and second inlets to the valve body are orientedat 90° from the first and second outlets from the body.